Tile Calculator

The short answer

A 12 by 12 inch tile covers one square foot, so 100 square feet of wall or floor needs 100 tiles plus waste. At 10 tiles per box that is 10 boxes, and ordering 10% extra brings it to 11 boxes. The waste allowance covers cuts at the perimeter, the first and last rows, and any pieces damaged in handling.

What it depends on

Layout changes the waste factor substantially. A straight lay needs 5 to 10%; a diagonal or herringbone pattern needs 15% or more because of the angle cuts and the greater offcut waste. Large-format tile needs a larger trowel notch and more mortar per square foot, and it is less forgiving of an uneven substrate — flatness requirements rise with tile size.

Where this stops being useful

This is a quantity estimate and does not cover mortar, adhesive, underlayment, movement joints or trim pieces, all of which add cost. Substrate flatness and moisture are the usual causes of failure, and wet areas have waterproofing requirements the tile does not satisfy on its own. General information and planning only, not engineering, structural or code advice.

Tile is sold by the box and boxes do not divide neatly into rooms, so the waste figure matters more here than for carpet. Ten percent is a reasonable allowance for a straightforward rectangular room laid square to the walls. It rises to fifteen percent or more where the room has diagonal cuts, a shower area with complex geometry, or a pattern that has to line up. Lay the tiles out on the floor before you order if the room is anything but rectangular — knowing where the cuts will fall tells you how many boxes you actually need, which is more reliable than any percentage.

Tile is the material where a dry layout is genuinely worth the time. Setting out a handful of tiles on the floor before the adhesive is mixed tells you where the cuts will fall, whether the centre lines will look intentional, and how many boxes you will actually open.

Grout quantity is calculated from the tile area and the joint width, and it is the step most people forget. Thinset or adhesive is also measured by area, and the coverage figure on the bag varies with the tile type and the trowel used. Plan the setting order before laying, because a tile job needs more setting time than most beginners expect and the floor cannot be walked on the same day. If you are tiling over an existing floor, add the demolition and preparation time separately — it often takes longer than the tiling itself.

Tiles are sold in fixed sizes and usually in boxes with a set number inside, so a tiling estimate eventually becomes a whole number of boxes. The arithmetic starts with the area to cover and the area of a single tile — a twelve-inch tile covers one square foot, a six-inch tile a quarter of that — but the number you finally buy is always higher than a straight division suggests, because tiles get cut and sometimes break. Waste comes from edges and corners. A wall or floor rarely divides exactly into whole tiles, so the tiles along the perimeter are cut, and the offcut is usually too small to use elsewhere. Diagonal layouts, borders and patterns create more waste than a simple grid. Ten per cent is a sensible default for a plain square layout; fifteen to twenty per cent is safer for large-format tiles, diagonal patterns or a novice doing the job. Large tiles deserve particular care. They cover more area each, so a single broken tile costs more, and they need a flatter substrate and wider joints. They also look best with fewer cuts, which often means planning the layout from the centre of the room outward rather than starting at a wall, and that planning changes how many tiles you actually consume. This calculator converts your area into tiles for the size you choose, adds a waste allowance and rounds up. It ignores the joint width, which slightly increases coverage, and assumes a simple layout. Always buy spares from the same batch, since tiles are fired in lots that can differ subtly in shade.

This calculator returns estimates for planning and general information only. It is not engineering, architectural, structural, electrical or code advice, and it cannot replace a qualified professional who has seen the site. Material quantities depend on the actual dimensions, the product you buy and local building codes, so confirm the figures before ordering materials or starting work, and always follow local regulations.